A handful of soil from a Nova Scotia park has yielded a potential new weapon against one of the nastiest superbugs around, a team of scientists led by McMaster University has found.

And the discovery comes not from cutting-edge technology but from a search of the environment and old-school microbiological methods, according to a new paper published in the journal Nature.

“It is a pleasantly surprising paper because a lot of people have been trying to find (something like this) and have come up empty,” said Kim Lewis, director of the Antimicrobial Discovery Center at Northeastern University, who was not involved with the study.

“This is a reminder of the richness of nature in producing antimicrobials.”

The phenomenon of antibiotic resistance is as old as antibiotics themselves but recent years have seen the emergence of superbugs with a powerful new defence: NDM-1, which stands for New Delhi metallo-beta-lactamase-1.

When armed with enzymes such as NDM-1, superbugs become what public health officials refer to as “nightmare bacteria” — pathogens that can overpower nearly every drug in the medicine cabinet, including carbapenems, which are considered antibiotics of last resort. According to the U.S. Centers for Disease Control and Prevention, carbapenem-destroying superbugs are particularly lethal, killing one in two patients who acquire infections in their bloodstreams.

NDM-1 was first reported in 2009 in a Swedish patient who was infected at a hospital in India. But these superbugs have since spread around the world and in Canada, NDM-1 has popped up everywhere from Toronto and Brampton to British Columbia. Since 2008, the Public Health Agency of Canada has tested 189 samples positive for NDM-1; roughly three quarters are from a recent outbreak at two B.C. hospitals, according to an agency spokesperson.

“(NDM-1) really is a sort of death star for that class of drug,” said microbiologist Gerry Wright, the senior author on the paper and director of the M.G. DeGroote Institute for Infectious Disease Research at McMaster University. “It was a nail in the coffin for many antibiotics. The only drugs available to treat infections by these organisms are some really toxic compounds.”

But Wright and his team have identified a molecule from a common fungus that appears to be very good at destroying NDM-1 — and, if all goes well, could offer a new therapy for drug-resistant infections.

This is not a new molecule, however; it was discovered nearly 50 years ago by scientists studying a mould that was causing plant leaves to wilt.

“That is exciting because it’s an old molecule,” said paper co-author Timothy Walsh, a professor at Cardiff University in Wales and the scientist who first discovered the NDM-1 gene. “It’s been known for a very long time and yet people have dismissed it as having any serious therapeutic value.”

During the “golden age” of antibiotics in the 1950s and ’60s, many drugs were discovered by scientists looking in the soil, where bacteria and fungi have been attacking each other with antibiotics since the beginning of time. The phenomenon of antibiotic resistance is just as old — after all, microbes that can survive these molecular missiles sent by their neighbours are the ones that end up dominating.

But no new classes of antibiotics have been discovered since the 1980s and most pharmaceutical companies have now largely abandoned the search. But as antibiotic resistance becomes an increasingly urgent problem — the World Health Organization has warned of a looming “post-antibiotic era” where something as simple as a scratch can once again kill — some researchers are turning back to nature in the quest for new drugs.

For the last decade or so, Wright has been building a “library” of micro-organisms found in soil samples collected across Canada. Any time a graduate student would go hiking or camping, Wright would ask them to bring back some soil in a Ziploc baggie.

One student returned from Nova Scotia’s Kejimkujik National Park with a soil sample that contained a strain of Aspergillus versicolor, a fungus commonly found in damp environments and mouldy homes.

From this fungus, Wright and his team isolated a molecule that could “knock out” NDM-1 — thus stripping these superbugs of their defences and giving antibiotics their offensive power back.

“It’s like Dave Semenko,” Wright explains, referencing the hockey enforcer many considered Wayne Gretzky’s bodyguard. “He clears the defence so Wayne Gretzky can charge the puck.”

To further test this molecule — called aspergillomarasemine A or AMA — Wright sent it to Walsh in the United Kingdom, where he tested it against a collection of 229 superbug strains that have infected patients around the world.

Not only did AMA work on 88 per cent of the NDM-1 strains, it was also effective on 90 per cent of strains producing VIM-2 — another enzyme that helps bacteria defeat last-resort antibiotics like carbapenems.

“Both of these are at the moment the global players in carbapenem resistance,” Walsh says. “So at that point I thought ‘we have something fairly special here.’”

Wright and his team have tested the molecule in superbug-infected mice and found that more than 95 per cent survived after receiving a single dose of AMA along with a carbapenem. They are now performing tests to see if the therapy would also be safe for humans.

But even if all goes well, it will be another ten years of development and clinical trials before this therapy reaches the market, Wright says. This molecule also won’t solve the wider problem of antibiotic resistance, adds Dr. Allison McGeer, an infectious disease specialist at Mount Sinai Hospital — bacteria have a constantly evolving arsenal of antibiotic-defeating strategies at their disposal.

But for McGeer, the results of this new study show “promise” — and proof that basic research can produce potentially life-saving results.

“Obviously we’re still a long way from doing things with this molecule but I think it opens up a whole new range of potential exploration,” she says. “It really gives one hope that we might be able to stay ahead of bacteria.”

More on thestar.com

We value respectful and thoughtful discussion. Readers are encouraged to flag comments that fail to meet the standards outlined in our
Community Code of Conduct.
For further information, including our legal guidelines, please see our full website
Terms and Conditions.